1. Technical Field
The present invention generally relates to display technology of organic light emitting diode (OLED) and, particularly to a pixel circuit and a pixel driving method.
2. Description of the Related Art
Usually, in an active matrix organic light emitting diode (OLED) display, a pixel is configured with transistors and a storage capacitor operatively to store charges and thereby control a brightness of OLED. Refer to FIG. 1, which shows a schematic diagram of a traditional pixel circuit. The pixel circuit 10 has a two-transistor and one-capacitor (2T1C) structure. The pixel circuit 10 includes a P-channel driving transistor M1, a P-channel switching transistor Ms, a storage capacitor Cst and an OLED 16. Two terminals of the storage capacitor Cst are respectively electrically connected to the gate electrode and the source electrode of the driving transistor M1. The source electrode of the driving transistor M1 is electrically coupled to a power supply voltage VDD. The drain electrode of the driving transistor M1 is electrically coupled to the anode of the OLED 16. The cathode of the OLED 16 is electrically coupled to another power supply voltage VSS. The gate electrode of the driving transistor M1 is electrically coupled to a data line DL through the switching transistor Ms and for receiving a data voltage Vdata from the data line DL. The gate electrode of the switching transistor Ms is electrically coupled to a scanning line SCAN, so that the on-off states of the switching transistor Ms can be controlled by the scanning line SCAN. Herein, the brightness of the OLED 16 can be changed by providing different data voltages Vdata.
However, for each pixel circuit of the active matrix OLED display, due to the impact caused by a threshold voltage shift of the transistors related to their manufacture process, material attenuation and/or operating time of the OLED, a pixel current of the pixel circuit must be compensated by adjusting the data voltage Vdata for getting a better brightness, so as to achieve good display effect. Therefore, for the purpose of effectively compensating the pixel current of the pixel circuit, the structure design of the pixel circuit and the driving method of the pixel circuit should be improved, so as to avoid abnormal display or compensation invalidation in the operation of the OLED display.